Anterior segment oculomics in systemic sclerosis: reduced OCT-derived pupil diameter without iris morphology...

Systemic sclerosis (SSc) is a multisystem autoimmune disease characterized by microvascular dysfunction and fibrosis. While posterior segment ocular involvement has been described, quantitative anterior segment alterations remain poorly characterized. The iris, as part of the uveal tract, shares vascular features with the choroid and may reflect systemic microvascular and autonomic dysregulation. Within the emerging framework of oculomics, anterior segment optical coherence tomography (AS-OCT)-derived iris and pupil metrics may represent accessible, non-invasive ocular features of systemic neurovascular health.

To compare static AS-OCT-derived pupil diameter, iris thickness, and iris cross-sectional area between patients with SSc and healthy controls, and to explore their associations with systemic and ocular parameters.

In this prospective cross-sectional study, 31 patients with SSc and 32 age- and sex-matched healthy controls underwent standardized AS-OCT imaging under controlled photopic conditions. Pupil diameter, iris thickness at 1, 2, and 3 mm from the pupil margin, and nasal and temporal iris cross-sectional areas up to 3 mm from the pupil margin were quantified using ImageJ software. Inter-rater reproducibility was assessed using intraclass correlation coefficients. Group comparisons and exploratory correlation and univariate regression analyses were performed.

Iris thickness and cross-sectional areas did not differ significantly between groups. Static AS-OCT-derived pupil diameter was smaller in the SSc group in the unadjusted comparison (p = 0.033); however, after adjustment for mean arterial pressure (MAP) this difference was no longer statistically significant, although the direction and magnitude of the effect were preserved (β = -366.9 μm, p = 0.057). In controls, pupil diameter correlated positively with selected iris parameters, whereas such associations were absent in SSc. Exploratory correlation and regression analyses did not provide consistent evidence of structural anterior uveal involvement.

Under standardized acquisition conditions, static AS-OCT pupil diameter tended to be smaller in patients with SSc, but this difference did not remain statistically significant after adjustment for MAP. Structural iris parameters did not differ between groups. This preliminary, hypothesis-generating finding may be consistent with functional rather than structural anterior segment alterations, but it does not directly demonstrate autonomic or neurovascular dysfunction and requires validation in larger cohorts, preferably with dynamic pupillometry.